Dynamic and Static Functional Gradient in Temporal Lobe Epilepsy With Hippocampal Sclerosis Versus Healthy Controls

Area of Science:

• Neuroscience
• Cognitive Science
• Medical Imaging

Background:

• The brain's intrinsic hierarchical architecture is represented by connectivity gradients.
• Previous research suggested but did not confirm the dynamic nature of these gradients.
• Cognitive impairment is frequently observed in temporal lobe epilepsy (TLE).

Purpose of the Study:

• To investigate the dynamics of the brain's principal gradient in TLE.
• To explore the neural correlates of cognitive decline in TLE using gradient techniques.
• To compare gradient features and task-based activation between TLE patients and healthy controls.

Main Methods:

• Functional MRI (fMRI) during a verbal fluency task was used.
• Thirty TLE patients and 29 healthy controls (HC) participated.
• Gradient techniques and sliding window approaches analyzed dynamic connectivity and activation patterns.

Main Results:

• TLE patients exhibited reduced dynamic gradient recruitment and atypical activation-gradient correlations.
• The principal gradient in TLE was contracted and its reconfiguration did not drive activation changes.
• Impaired neural activation and gradient dynamics correlated with cognitive deficits in TLE.

Conclusions:

• The principal brain gradient is dynamic and is disrupted in TLE.
• TLE alters activation patterns, the principal gradient, and its dynamics.
• These disruptions are significantly correlated with cognitive decline in TLE patients.